Variabilidade atmosférica associada a casos extremos de precipitação na Região Sudeste do Brasil / Atmospheric variability associated to estreme precipitation events over southeast region of Brazil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The most severe climate impacts on the society occur due to climate variability and extreme precipitation events. Therefore, their study on various space and time scales are important to determine, in details, the related aspects and thus to provide information to analyze their representations in numerical forecast models. The goal of this work is to study various scales influence on extreme precipitation events over part of Southeast Region of Brazil, which comprises the Serra do Mar region. The precipitation climatology and large scale characteristics of the rainiest and driest years over this area were studied. The large scale characteristics of daily extreme events which occurred in the rainiest months and seasons were also studied. Two extreme precipitation events were simulated with Eta model to analyze the model performance and the mesoscale influence in such extreme events. Analysing the precipitation climatology, the results indicated a summer to winter precipitation reduction and that the extremes are becoming more frequent. The frequency of wet springs and summers have increased with time, and the frequency of dry autumns and winters, also increased with time during the analyzed period. In the summer, the SACZ configuration was identified as the major contributor to precipitation and, in the winter, frontal systems make this role. The results suggest the influence of a geopotential sea-saw between polar and middle latitudes, similar to the AAO, on the analyzed region, changing signs between dry and wet years; patterns of wavenumber four, three and two; PSA wavetrain pattern; features of MJO near equator and relations of convection over Australia and SPCZ with convection in the SACZ region. In the daily variability analysis, the influence of PSA and MJO configuration was also observed. In the extreme daily cases which occurred in the winter, a well organized wave four pattern was identified, while in the summer cases, a wavetrain from Indian Ocean to the Pacific was more evident. Atmospheric characteristics associated with two extreme precipitation cases over Serra do Mar were well simulated by the Regional Eta Model, as well as the intense observed precipitation, although with a slight displacement. Mesoscale features could be analyzed in the high resolution model outputs, such as the sea breeze, which contributed to the intense precipitation near the coast, enhancing the influence of the frontal systems. High values of instability indexes were also obtained from the model results.

ASSUNTO(S)

meteorologia antartic oscillation southeast region of brazil precipitation teleconnections região sudeste do brasil teleconexões oscilação antártica variabilidade atmosférica atmospheric variability precipitação

ACESSO AO ARTIGO

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